Projector Throw Distance Calculator
Calculate the ideal projector placement distance for any screen size, or find what screen size you'll get at a given distance.
Works for any throw ratio.
What Is Throw Ratio? Throw ratio is the most important specification when planning a projector installation. It is defined as the ratio of throw distance (the distance from the projector lens to the screen) to the screen width. A throw ratio of 1.5:1 means the projector must be placed 1.5 feet away for every 1 foot of screen width. A projector with a 1.5 throw ratio and a 100-inch wide screen must be placed 150 inches (12.5 feet) from the screen.
Projector Types by Throw Ratio Standard throw projectors have ratios of 1.2 to 2.0 and are the most common type for home theaters and classrooms. Short-throw projectors have ratios of 0.4 to 1.0 and can create large images from just a few feet away — ideal for small rooms. Ultra-short-throw (UST) projectors have ratios below 0.4 (often 0.2–0.3) and sit just inches from the wall, perfect for living rooms where a ceiling mount is impractical. Long-throw projectors with ratios above 2.0 are used in large auditoriums, churches, and stadiums.
Screen Size Is Measured Diagonally When a screen is described as “100 inches,” that measurement is the diagonal. For a 16:9 aspect ratio screen, the actual width is 87.2 inches and the height is 49.1 inches. The throw ratio formula uses width, not diagonal — so always work from the width. This calculator converts diagonal screen sizes to width automatically.
16:9 Is the Universal Modern Aspect Ratio Nearly all modern projectors, TVs, and computer content is 16:9 (widescreen). This means screen height is always screen width divided by 1.778 (16÷9 = 1.778). If you’re showing 4:3 content (older video games, legacy slideshows) on a 16:9 screen, you’ll have black bars on the sides.
Lumens and Ambient Light Screen size is useless without enough brightness. A dark home theater room needs 1,000–1,500 ANSI lumens. A room with some ambient light needs 2,000–3,000 lumens. A bright conference room or classroom needs 3,000+ lumens. As screen size increases, the projected image becomes dimmer (brightness is spread over more area) — so larger screens demand more lumens.